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Abstract:

A subframe for a vehicle satisfies durability and crash performance of a
rear mounting portion during vehicle crash. The subframe may include an
upper reinforcement and a lower reinforcement, which are spaced apart
from each other and assembled to the subframe, and a rear mounting
bracket connected to a chassis via a mounting bolt, wherein the lower
reinforcement includes a bolt pushing-inducing trim line connected to a
bolt hole and the upper reinforcement includes a pair of
deformation-inducing holes formed on both front and rear of a pipe nut
such that the mounting bolt is separated from an initial position and the
upper reinforcement is deformed when an impact load is applied.

Claims:

1. A subframe for a vehicle, the subframe comprising an upper
reinforcement and a lower reinforcement, which are spaced apart from each
other and assembled to the subframe, and a rear mounting bracket
connected to a chassis via a mounting bolt, wherein the lower
reinforcement comprises a trim line connected to a bolt hole and the
upper reinforcement comprises a pair of deformation-inducing holes formed
on both front and rear of a pipe nut such that the mounting bolt is
separated from an initial position and the upper reinforcement is
deformed upon impact.

2. The subframe of claim 1, wherein the trim line is configured to extend
to the most adjacent edge of the lower reinforcement to open one side of
the lower reinforcement.

3. The subframe of claim 1, wherein the deformation-inducing holes
comprise a first hole formed with a width similar or corresponding to
that of the pipe nut in the left and right direction and a second hole
formed on the opposite side of the first hole with a width similar or
corresponding to that of the body of the mounting bolt in the left and
right direction.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims under 35 U.S.C. §119(a) the benefit of
Korean Patent Application No. 10-2011-0044314 filed May 12, 2011, the
entire contents of which application is incorporated herein for all
purposes by this reference.

BACKGROUND OF INVENTION

[0002] 1. Field of Invention

[0003] The present invention relates to a subframe for a vehicle. More
particularly, it relates to a subframe for a vehicle, which satisfies
durability and crash performance of a rear mounting portion during
vehicle crash.

[0004] 2. Background Art

[0005] In general, a vehicle body comprises suitable combinations of
various panels and frames. Especially, a frame structure of the vehicle
body has a great influence on the structural stiffness, and thus various
types of structures are proposed for the vehicle body to efficiently
disperse and absorb the impact applied to the vehicle body during running
or during crash.

[0006] In a conventional four-wheel drive vehicle, as shown in FIG. 1, a
rear vehicle body comprises a subframe 1 to which a damper and the like
is connected, a side frame 8 connected to both sides of the subframe 1
via a mounting member and extending in the longitudinal direction of the
vehicle body, etc.

[0007] The conventional subframe is connected to a chassis via a rear
mounting bracket. In order to solve the problem that the rear mounting
bracket is being torn during a vehicle crash, a reinforcement is added to
an area with minimum stress index in the rear mounting bracket (i.e., the
most vulnerable area during analysis of durability performance).

[0008] In a conventional rear mounting bracket 2 of a subframe as shown in
FIG. 2, an upper reinforcement 3 and a lower reinforcement 4 are provided
to be spaced apart from each other and arranged up and down to improve
the durability of the rear mounting bracket 2 as shown in FIG. 3.
Moreover, a mounting member 6 is provided to assemble a lower pipe 5,
which is welded between the upper reinforcement 3 and the lower
reinforcement 4, and the rear mounting bracket 2 to a chassis 9.

[0009] However, the conventional subframe has the problem that the
vehicle's pulse (or the vehicle's pulse severity) occurring due to impact
load applied to the vehicle during crash is increased by the
reinforcement of the rear mounting bracket provided to improve the
durability thereof, which in turn increases the risk of occupant injury,
thus reducing the crash performance.

[0010] The information disclosed in this Background section is only for
enhancement of understanding of the general background of the invention
and should not be taken as an acknowledgement or any form of suggestion
that this information forms the prior art already known to a person
skilled in the art.

SUMMARY OF INVENTION

[0011] Various aspects of the present invention provide for a subframe for
a vehicle, which satisfies durability and crash performance of a rear
mounting portion in a manner that a lower reinforcement is configured to
have a structure capable of changing the position of a mounting bolt
assembled to a chassis and an upper reinforcement is configured to have a
structure capable of inducing self-deformation during vehicle crash.

[0012] In some aspects, the present invention provides a subframe for a
vehicle, the subframe comprising an upper reinforcement and a lower
reinforcement, which are spaced apart from each other and assembled to
the subframe, and a rear mounting bracket connected to a chassis via a
mounting bolt, wherein the lower reinforcement comprises a bolt
pushing-inducing trim line connected to a bolt hole and the upper
reinforcement comprises a pair of deformation-inducing holes formed on
both front and rear of a pipe nut such that the mounting bolt is
separated from an initial position and the upper reinforcement is
deformed when an impact load is applied.

[0013] In various aspects of the present invention, the bolt
pushing-inducing trim line is configured to extend to the most adjacent
edge of the lower reinforcement to open one side of the lower
reinforcement.

[0014] In other aspects of the present invention, the deformation-inducing
holes comprise a first hole formed with a width similar or corresponding
to that of the pipe nut in the left and right direction and a second hole
formed on the opposite side of the first hole with a width similar or
corresponding to that of the body of the mounting bolt in the left and
right direction.

[0015] It is understood that the term "vehicle" or "vehicular" or other
similar term as used herein is inclusive of motor vehicles in general
such as passenger automobiles including sports utility vehicles (SUV),
buses, trucks, various commercial vehicles, watercraft including a
variety of boats and ships, aircraft, and the like, and includes hybrid
vehicles, electric vehicles, plug-in hybrid electric vehicles,
hydrogen-powered vehicles and other alternative fuel vehicles (e.g.,
fuels derived from resources other than petroleum). As referred to
herein, a hybrid vehicle is a vehicle that has two or more sources of
power, for example both gasoline-powered and electric-powered vehicles.

[0016] The methods and apparatuses of the present invention have other
features and advantages which will be apparent from or are set forth in
more detail in the accompanying drawings, which are incorporated herein,
and the following Detailed Description, which together serve to explain
certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a diagram showing a rear mounting portion of a
conventional subframe for a vehicle.

[0018]FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1.

[0019] FIG. 3 is a perspective view showing an upper reinforcement and a
lower reinforcement of FIG. 2.

[0020] FIG. 4 is an exploded perspective view showing the configuration of
an exemplary rear mounting portion of a subframe for a vehicle in
accordance with the present invention.

[0021] FIG. 5 is an assembled perspective view showing the configuration
of an exemplary rear mounting portion of a subframe for a vehicle in
accordance with the present invention.

[0022] FIG. 6 is a cross-sectional view taken along line B-B of FIG. 5.

[0023] FIG. 7 is a perspective view showing an exemplary upper
reinforcement and lower reinforcement in accordance with the present
invention.

[0024] FIG. 8 is a diagram showing the results of analysis of an exemplary
vehicle's pulse severity in accordance with the Test Example of the
present invention.

[0025] It should be understood that the appended drawings are not
necessarily to scale, presenting a somewhat simplified representation of
various preferred features illustrative of the basic principles of the
invention. The specific design features of the present invention as
disclosed herein, including, for example, specific dimensions,
orientations, locations, and shapes will be determined in part by the
particular intended application and use environment.

[0026] In the figures, reference numbers refer to the same or equivalent
parts of the present invention throughout the several figures of the
drawing.

DETAILED DESCRIPTION

[0027] Reference will now be made in detail to various embodiments of the
present invention(s), examples of which are illustrated in the
accompanying drawings and described below. While the invention(s) will be
described in conjunction with exemplary embodiments, it will be
understood that present description is not intended to limit the
invention(s) to those exemplary embodiments. On the contrary, the
invention(s) is/are intended to cover not only the exemplary embodiments,
but also various alternatives, modifications, equivalents and other
embodiments, which may be included within the spirit and scope of the
invention as defined by the appended claims.

[0028] Various embodiments of the present invention provide a subframe
provided at the bottom of a vehicle, which can satisfy durability and
crash performance by modifying a rear mounting portion, i.e., a rear
mounting bracket, of the subframe to which reinforcements are added and
which has conventionally caused deterioration of crash performance.

[0029] As shown in FIG. 4, a subframe in accordance with various
embodiments of the present invention is connected to a chassis 9 of a
vehicle via a rear mounting bracket 10 provided at one side thereof, and
reinforcements 11 and 14 as shown in detail in FIG. 7 are provided in the
rear mounting bracket 10 to improve durability.

[0030] As shown in FIG. 6, the reinforcements 11 and 14 comprise a lower
reinforcement 11 attached closely to the rear mounting bracket 10 and an
upper reinforcement 14 spaced a predetermined distance from the lower
reinforcement 11 and assembled to the rear mounting bracket 10.

[0031] That is, the upper reinforcement 14 and the lower reinforcement 11
are arranged up and down in a predetermined region of the rear mounting
bracket 10.

[0032] A lower pipe 16 penetrating the upper reinforcement 14 is placed on
the lower reinforcement 11 and welded to the upper reinforcement 14. The
lower reinforcement 11 and the lower pipe 16 are connected to each other
via a noise-proof sealer, for example.

[0033] Moreover, a pipe nut 17 is welded to the top of the upper
reinforcement 14 and connected to a mounting bolt 18, which penetrates
the chassis 9, the rear mounting bracket 10, the reinforcements 11 and
14, and the lower pipe 16, such that the rear mounting bracket 10 is
assembled to the chassis 9.

[0034] That is, the rear mounting bracket 10 to which the reinforcements
11 and 14 are assembled is connected to the chassis 9 via the mounting
bolt 18 and the pipe nut 17.

[0035] Meanwhile, as shown in FIG. 7, the lower reinforcement 11 comprises
a bolt pushing-inducing trim line 13 connected to a bolt hole 12 through
which the mounting bolt 18 penetrates.

[0036] The bolt pushing-inducing trim line (hereinafter, referred to as a
trim line) 13 is configured to have a structure capable of absorbing
impact in such a manner that the mounting bolt 18 is pushed and moved by
an impact load during vehicle crash. The trim line 13 may extend from the
bolt hole 12 to the edge of the lower reinforcement 11.

[0037] Preferably, the trim line 13 starts from one side of the bolt hole
12 and extends to the other side on the edge of the lower reinforcement
11, thereby opening one side of the lower reinforcement 11.

[0038] Therefore, the mounting bolt 18 is moved from the initial position
along the trim line 13 when the impact load is applied, thus absorbing
impact energy. Moreover, the mounting bolt 18 may be separated from the
lower reinforcement 11 or from the rear mounting bracket 10 depending on
the magnitude of the impact energy.

[0039] That is, when the mounting bolt 18 is pushed and moved along the
trim line 13, it can be moved and separated from the initial position
depending on the magnitude of the impact energy, thereby enhancing the
effect of impact absorption.

[0040] Moreover, the trim line 13 has a width smaller than that of the
mounting bolt 18 such that the mounting bolt 18 pushes the lower
reinforcement 11 on both sides of the trim line 13 from side to side when
it is moved.

[0041] In other words, the trim line 13 can absorb the impact energy in a
manner that the mounting bolt 18 receiving the impact load is moved
and/or separated from the initial position along the trim line 13, not in
a manner that the mounting bolt 18 receiving the impact load is certainly
separated from the lower reinforcement 11 or from the rear mounting
bracket 10.

[0042] That is, the trim line 13 can absorb the impact energy during crash
by the position change of the mounting bolt 18 itself, even when the
mounting bolt 18 is not completely separated from the lower reinforcement
11 or from the rear mounting bracket 10.

[0043] Moreover, the upper reinforcement 14 comprises a pair of bracket
deformation-inducing holes 15 having a slit shape and formed on both
front and rear of the pipe nut 17 to induce deformation of the upper
reinforcement 14 when an impact load is applied thereto.

[0044] The bracket deformation-inducing holes (hereinafter, referred to as
deformation-inducing holes) 15 allow the upper reinforcement 14 itself to
be torn or deformed such that the rear mounting bracket 10 is deformed,
thus absorbing the impact energy. Accordingly, the deformation-inducing
holes 15 are formed in optimal positions.

[0045] For example, the deformation-inducing holes 15 may comprise a first
hole 15a formed with a width similar or corresponding to that of the pipe
nut 17 in the left and right direction and a second hole 15b formed on
the opposite side of the first hole 15a with a width similar or
corresponding to that of the body of the mounting bolt 18 in the left and
right direction.

[0046] Therefore, the upper reinforcement 14 can be easily crushed or torn
more than the absence of the deformation-inducing holes 15 during crash,
thereby efficiently absorbing the impact energy.

[0047] As such, with the improved structure of the rear mounting portion
of the subframe according to the present invention, it is possible to
allow the upper reinforcement to be deformed and the mounting bolt to be
pushed backward against the impact load, thereby absorbing the impact
energy.

[0048] That is, the vehicle's pulse (or the vehicle's pulse severity)
occurring due to an impact load applied to the vehicle during crash is
reduced, which in turn reduces the risk of occupant injury, thus
improving the crash performance. As a result, the subframe of the present
invention can satisfy durability and crash performance to meet the NCAP
ratings.

[0049] Next, the effects of the present invention will be described in
detail through the results of analysis of the durability of the subframe
and the vehicle's pulse.

EXAMPLE

[0050] As starting components to be assembled to a rear mounting bracket
of a subframe, an upper reinforcement and a lower reinforcement with a
structure shown in FIG. 7 and Table 1 were manufactured.

Comparative Example 1

[0051] As starting components to be assembled to a rear mounting bracket
of a subframe, an upper reinforcement and a lower reinforcement with a
structure shown in FIG. 3 and Table 1 were manufactured.

Comparative Example 2

[0052] As starting components to be assembled to a rear mounting bracket
of a subframe, an upper reinforcement and a lower reinforcement with a
structure shown in Table 1 were manufactured.

Test Example

[0053] After each of the reinforcements in the Example and Comparative
Example 1 and 2 was mounted on a rear mounting portion of a front
subframe for a vehicle under the same conditions, a crash test was
performed on each vehicle under the same conditions, and the durability
and crash performance were evaluated.

[0054] Braking and cornering under a load of 1 G using a virtual test
laboratory (VTL) was applied to each rear mounting portion of the
subframe employing the reinforcements in the Example and Comparative
Example 1 and 2 to evaluate the stress index. Moreover, the durability
index of each rear mounting portion was evaluated by BIG durability
analysis and X C durability analysis, and the results are shown in FIG. 8
and Tables 1 and 2.

[0055] FIG. 8 is a diagram showing the results of the vehicle's pulse
severity due to an impact load applied to each vehicle.

[0056] As shown in Table 1, it can be seen from the results of the Test
Example that all of the Example and Comparative Examples 1 and 2
satisfied the stress index of more than LO and the durability index of
more than 1.0.

[0057] As shown in Table 2, while the Example satisfied the vehicle's
pulse severity at a target value of less than 55%, Comparative Examples 1
and 2 did not satisfy the target value of the vehicle's pulse severity,
from which it can be seen that only the Example according to the present
invention satisfied the requirements for occupant injury.

[0058] Especially, as can be seen from the graph of FIG. 8 showing the
results of the analysis of the vehicle's pulse severity, while
Comparative Examples 1 and 2 showed the maximum value of the vehicle's
pulse near the time of 0.035 seconds, the Example significantly reduced
the vehicle's pulse near the time of 0.035 seconds.

[0059] Moreover, in the case of Comparative Examples 1 and 2, the mounting
bolt was not separated from the subframe, however, in the case of the
Example, the mounting bolt was pushed on the subframe by the impact load,
and thus its position was moved.

[0060] It can be seen from the analysis of the durability and the
vehicle's pulse severity that the dynamic displacement of the vehicle was
increased by the structure according to the present invention applied to
the rear mounting portion of the subframe during vehicle crash, and thus
the vehicle's pulse severity was reduced.

[0061] As the pulse severity was significantly reduced, the risk of
occupant injury during crash was reduced, and thus the front crash rating
in the US NCAP crash tests was increased and the target of the general
rating was achieved.

[0062] As such, according to the present invention, the mounting bolt was
moved from the initial position together with the deformation of the
upper reinforcement, which reduced the risk of occupant injury, thus
achieving the NCAP vehicle safety rating, compared to the case where the
mounting bolt was completely separated from the subframe.

[0063] As described above, the subframe for a vehicle according to the
present invention can reduce the vehicle's pulse severity occurring due
to an impact load, which in turn reduces the risk of occupant injury,
thus satisfying the durability and crash performance, by modifying the
rear mounting portion of the subframe to which the reinforcements are
added and which has conventionally caused deterioration of crash
performance.

[0064] For convenience in explanation and accurate definition in the
appended claims, the terms upper or lower, front or rear, and etc. are
used to describe features of the exemplary embodiments with reference to
the positions of such features as displayed in the figures.

[0065] The foregoing descriptions of specific exemplary embodiments of the
present invention have been presented for purposes of illustration and
description. They are not intended to be exhaustive or to limit the
invention to the precise forms disclosed, and obviously many
modifications and variations are possible in light of the above
teachings. The exemplary embodiments were chosen and described in order
to explain certain principles of the invention and their practical
application, to thereby enable others skilled in the art to make and
utilize various exemplary embodiments of the present invention, as well
as various alternatives and modifications thereof. It is intended that
the scope of the invention be defined by the Claims appended hereto and
their equivalents.